This invention relates to an apparatus for viewing an original and projecting an image thereof onto a moving imaging surface, and to multi-mode reproducing apparatus preferably of the electrostatographic type.
A variety of electrostatographic reproducing machines are commercially employed which have different modes of operation. One type of machine utilizes a moving original exposure system wherein an original document is moved past a fixed slit optical system for projecting an image onto the moving photoconductive surface. These machines include a means for changing the magnification of the projected image to provide reduction copies. Exemplary of patents in this area is U.S. Pat. No. 3,076,392, to Cerasani et al.
Other machines have been adapted to copy stationary original documents at a variety of magnifications or reductions through the use of a scanning optical system. Exemplary of patents in this area are U.S. Pat. Nos. 3,476,478, to Rees, Jr.; 3,542,467 to Furgeson; 3,614,222 to Post; and 3,837,743 to Amemiya. Another approach which has been utilized for projecting images for reproduction at varying magnifications from a stationary original comprises full frame exposure. Exemplary of patents in this area are U.S. Pat. Nos. 3,543,289 to Koizumi; 3,687,544 to Muller; 3,703,334 to Knechtel; and German Offenlegungsschrift 2,154,944 to Libby.
U.S. Pat. Nos. 3,703,334 to Knechtel and 3,837,743 to Amemiya set forth above are also significant in that they disclose the use of a separate reflector or add reflectors, respectively which are selectively positionable in the optical path for changing the conjugate distance of the optical system for providing varying magnifications.
The aforenoted machines are adapted to provide one or more modes of copying having different magnifications. Other forms of multi-mode copiers are available commerically. For example, in the Xerox 3100 LDC machine an optical system is provided which enables the machine to copy from a stationary original in a first scanning mode or from a moving original in a second fixed optical mode. This latter mode being particularly adapted for copying documents larger than the conventional viewing platen size. U.S. Pat. No. 3,877,804 to Hoppner is illustrative of a machine similar in many respects to the 3100 LDC machine.
Reproducing apparatuses including the capability of making copies from both moving and stationary originals are also described in U.S. Pat. No. 3,833,296 to Vola and in IBM Technical Disclosure Bulletin, Vol. 12, No. 1, at page 173, June 1969.
It has been found desirable to provide multi-mode reproducing apparatus having the unique features of the 3100 LDC machine including its extremely compact size, but also having the capability of reduction copying.
When one attempts to employ a multi-mode optical system in a highly compact environment difficulties arise such as vignetting. Vignetting comprises the loss of a portion of the image through the interference in the optical path of one or more elements within the optical cavity. For example, mirror carriages frame elements in the optical cavity interfere with the light paths and block portions of them thereby reducing the quality of the resulting image. With a compact optical system it is difficult to provide multiple lens positions and other optical elements and frames in an arrangement wherein vignetting will not pose a serious problem.